/* * linux/ipc/shm.c * Copyright (C) 1992, 1993 Krishna Balasubramanian * Many improvements/fixes by Bruno Haible. * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994. * Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli. * * /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie * BIGMEM support, Andrea Arcangeli * SMP thread shm, Jean-Luc Boyard * HIGHMEM support, Ingo Molnar * avoid vmalloc and make shmmax, shmall, shmmni sysctl'able, * Christoph Rohland */ #include #include #include #include #include #include #include #include #include #include #include #include #include "util.h" struct shmid_kernel /* extend struct shmis_ds with private fields */ { struct shmid_ds u; unsigned long shm_npages; /* size of segment (pages) */ pte_t **shm_dir; /* ptr to array of ptrs to frames -> SHMMAX */ struct vm_area_struct *attaches; /* descriptors for attaches */ int id; /* backreference to id for shm_close */ struct semaphore sem; }; static int findkey (key_t key); static int newseg (key_t key, int shmflg, size_t size); static int shm_map (struct vm_area_struct *shmd); static void killseg (int id); static void shm_open (struct vm_area_struct *shmd); static void shm_close (struct vm_area_struct *shmd); static struct page * shm_nopage(struct vm_area_struct *, unsigned long, int); static int shm_swapout(struct page *, struct file *); #ifdef CONFIG_PROC_FS static int sysvipc_shm_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data); #endif unsigned int shm_prm[3] = {SHMMAX, SHMALL, SHMMNI}; static int shm_tot = 0; /* total number of shared memory pages */ static int shm_rss = 0; /* number of shared memory pages that are in memory */ static int shm_swp = 0; /* number of shared memory pages that are in swap */ static int max_shmid = -1; /* every used id is <= max_shmid */ static DECLARE_WAIT_QUEUE_HEAD(shm_wait); /* calling findkey() may need to wait */ static struct shmid_kernel **shm_segs = NULL; static unsigned int num_segs = 0; static unsigned short shm_seq = 0; /* incremented, for recognizing stale ids */ /* locks order: shm_lock -> pagecache_lock (end of shm_swap) shp->sem -> other spinlocks (shm_nopage) */ spinlock_t shm_lock = SPIN_LOCK_UNLOCKED; /* some statistics */ static ulong swap_attempts = 0; static ulong swap_successes = 0; static ulong used_segs = 0; void __init shm_init (void) { #ifdef CONFIG_PROC_FS create_proc_read_entry("sysvipc/shm", 0, 0, sysvipc_shm_read_proc, NULL); #endif return; } #define SHM_ENTRY(shp, index) (shp)->shm_dir[(index)/PTRS_PER_PTE][(index)%PTRS_PER_PTE] static pte_t **shm_alloc(unsigned long pages) { unsigned short dir = pages / PTRS_PER_PTE; unsigned short last = pages % PTRS_PER_PTE; pte_t **ret, **ptr; ret = kmalloc ((dir+1) * sizeof(pte_t *), GFP_KERNEL); if (!ret) goto out; for (ptr = ret; ptr < ret+dir ; ptr++) { *ptr = (pte_t *)__get_free_page (GFP_KERNEL); if (!*ptr) goto free; memset (*ptr, 0, PAGE_SIZE); } /* The last one is probably not of PAGE_SIZE: we use kmalloc */ if (last) { *ptr = kmalloc (last*sizeof(pte_t), GFP_KERNEL); if (!*ptr) goto free; memset (*ptr, 0, last*sizeof(pte_t)); } out: return ret; free: /* The last failed: we decrement first */ while (--ptr >= ret) free_page ((unsigned long)*ptr); kfree (ret); return NULL; } static void shm_free(pte_t** dir, unsigned long pages) { pte_t **ptr = dir+pages/PTRS_PER_PTE; /* first the last page */ if (pages%PTRS_PER_PTE) kfree (*ptr); /* now the whole pages */ while (--ptr >= dir) free_page ((unsigned long)*ptr); /* Now the indirect block */ kfree (dir); } static int shm_expand (unsigned int size) { int id; struct shmid_kernel ** new_array; spin_unlock(&shm_lock); new_array = kmalloc (size * sizeof(struct shmid_kernel *), GFP_KERNEL); spin_lock(&shm_lock); if (!new_array) return -ENOMEM; if (size <= num_segs){ /* We check this after kmalloc so nobody changes num_segs afterwards */ /* * We never shrink the segment. If we shrink we have to * check for stale handles in newseg */ kfree (new_array); return 0; } if (num_segs) { memcpy (new_array, shm_segs, size*sizeof(struct shmid_kernel *)); kfree (shm_segs); } for (id = num_segs; id < size; id++) new_array[id] = (void *) IPC_UNUSED; shm_segs = new_array; num_segs = size; return 0; } static int findkey (key_t key) { int id; struct shmid_kernel *shp; if (!num_segs) return -1; for (id = 0; id <= max_shmid; id++) { if ((shp = shm_segs[id]) == IPC_NOID) { DECLARE_WAITQUEUE(wait, current); add_wait_queue(&shm_wait, &wait); for(;;) { set_current_state(TASK_UNINTERRUPTIBLE); if ((shp = shm_segs[id]) != IPC_NOID) break; spin_unlock(&shm_lock); schedule(); spin_lock(&shm_lock); } __set_current_state(TASK_RUNNING); remove_wait_queue(&shm_wait, &wait); } if (shp != IPC_UNUSED && key == shp->u.shm_perm.key) return id; } return -1; } /* * allocate new shmid_kernel and pgtable. protected by shm_segs[id] = NOID. * This has to be called with the shm_lock held */ static int newseg (key_t key, int shmflg, size_t size) { struct shmid_kernel *shp; int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT; int id, err; unsigned int shmall, shmmni; shmall = shm_prm[1]; shmmni = shm_prm[2]; if (shmmni > IPCMNI) { printk ("shmmni reset to max of %u\n", IPCMNI); shmmni = shm_prm[2] = IPCMNI; } if (shmmni < used_segs) return -ENOSPC; if ((err = shm_expand (shmmni))) return err; if (size < SHMMIN) return -EINVAL; if (shm_tot + numpages >= shmall) return -ENOSPC; for (id = 0; id < num_segs; id++) if (shm_segs[id] == IPC_UNUSED) { shm_segs[id] = (struct shmid_kernel *) IPC_NOID; goto found; } return -ENOSPC; found: spin_unlock(&shm_lock); shp = (struct shmid_kernel *) kmalloc (sizeof (*shp), GFP_KERNEL); if (!shp) { spin_lock(&shm_lock); shm_segs[id] = (struct shmid_kernel *) IPC_UNUSED; wake_up (&shm_wait); return -ENOMEM; } shp->shm_dir = shm_alloc (numpages); if (!shp->shm_dir) { kfree(shp); spin_lock(&shm_lock); shm_segs[id] = (struct shmid_kernel *) IPC_UNUSED; wake_up (&shm_wait); return -ENOMEM; } shp->u.shm_perm.key = key; shp->u.shm_perm.mode = (shmflg & S_IRWXUGO); shp->u.shm_perm.cuid = shp->u.shm_perm.uid = current->euid; shp->u.shm_perm.cgid = shp->u.shm_perm.gid = current->egid; shp->u.shm_segsz = size; shp->u.shm_cpid = current->pid; shp->attaches = NULL; shp->u.shm_lpid = shp->u.shm_nattch = 0; shp->u.shm_atime = shp->u.shm_dtime = 0; shp->u.shm_ctime = CURRENT_TIME; shp->shm_npages = numpages; shp->id = id; init_MUTEX(&shp->sem); spin_lock(&shm_lock); shm_tot += numpages; shp->u.shm_perm.seq = shm_seq; if (id > max_shmid) max_shmid = id; shm_segs[id] = shp; used_segs++; wake_up (&shm_wait); return (unsigned int) shp->u.shm_perm.seq * IPCMNI + id; } asmlinkage long sys_shmget (key_t key, size_t size, int shmflg) { struct shmid_kernel *shp; int err, id = 0; size_t shmmax; shmmax = shm_prm[0]; if (size > shmmax) return -EINVAL; down(¤t->mm->mmap_sem); spin_lock(&shm_lock); if (key == IPC_PRIVATE) { err = newseg(key, shmflg, size); } else if ((id = findkey (key)) == -1) { if (!(shmflg & IPC_CREAT)) err = -ENOENT; else err = newseg(key, shmflg, size); } else if ((shmflg & IPC_CREAT) && (shmflg & IPC_EXCL)) { err = -EEXIST; } else { shp = shm_segs[id]; if (shp->u.shm_perm.mode & SHM_DEST) err = -EIDRM; else if (size > shp->u.shm_segsz) err = -EINVAL; else if (ipcperms (&shp->u.shm_perm, shmflg)) err = -EACCES; else err = (int) shp->u.shm_perm.seq * IPCMNI + id; } spin_unlock(&shm_lock); up(¤t->mm->mmap_sem); return err; } /* * Only called after testing nattch and SHM_DEST. * Here pages, pgtable and shmid_kernel are freed. */ static void killseg (int id) { struct shmid_kernel *shp; int i, numpages; int rss, swp; shp = shm_segs[id]; if (shp == IPC_NOID || shp == IPC_UNUSED) BUG(); shp->u.shm_perm.seq++; /* for shmat */ shm_seq = (shm_seq+1) % ((unsigned)(1<<31)/IPCMNI); /* increment, but avoid overflow */ shm_segs[id] = (struct shmid_kernel *) IPC_UNUSED; used_segs--; if (id == max_shmid) while (max_shmid-- > 0 && (shm_segs[max_shmid] == IPC_UNUSED)); if (!shp->shm_dir) BUG(); spin_unlock(&shm_lock); numpages = shp->shm_npages; for (i = 0, rss = 0, swp = 0; i < numpages ; i++) { pte_t pte; pte = SHM_ENTRY (shp,i); if (pte_none(pte)) continue; if (pte_present(pte)) { __free_page (pte_page(pte)); rss++; } else { lock_kernel(); swap_free(pte_to_swp_entry(pte)); unlock_kernel(); swp++; } } shm_free (shp->shm_dir, numpages); kfree(shp); spin_lock(&shm_lock); shm_rss -= rss; shm_swp -= swp; shm_tot -= numpages; return; } asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds *buf) { struct shmid_ds tbuf; struct shmid_kernel *shp; struct ipc_perm *ipcp; int id, err = -EINVAL; if (cmd < 0 || shmid < 0) goto out_unlocked; if (cmd == IPC_SET) { err = -EFAULT; if(copy_from_user (&tbuf, buf, sizeof (*buf))) goto out_unlocked; } spin_lock(&shm_lock); switch (cmd) { /* replace with proc interface ? */ case IPC_INFO: { struct shminfo shminfo; spin_unlock(&shm_lock); err = -EFAULT; if (!buf) goto out; shminfo.shmmni = shminfo.shmseg = shm_prm[2]; shminfo.shmmax = shm_prm[0]; shminfo.shmall = shm_prm[1]; shminfo.shmmin = SHMMIN; if(copy_to_user (buf, &shminfo, sizeof(struct shminfo))) goto out_unlocked; spin_lock(&shm_lock); err = max_shmid < 0 ? 0 : max_shmid; goto out; } case SHM_INFO: { struct shm_info shm_info; err = -EFAULT; shm_info.used_ids = used_segs; shm_info.shm_rss = shm_rss; shm_info.shm_tot = shm_tot; shm_info.shm_swp = shm_swp; shm_info.swap_attempts = swap_attempts; shm_info.swap_successes = swap_successes; spin_unlock(&shm_lock); if(copy_to_user (buf, &shm_info, sizeof(shm_info))) goto out_unlocked; spin_lock(&shm_lock); err = max_shmid < 0 ? 0 : max_shmid; goto out; } case SHM_STAT: err = -EINVAL; if (shmid > max_shmid) goto out; shp = shm_segs[shmid]; if (shp == IPC_UNUSED || shp == IPC_NOID) goto out; if (ipcperms (&shp->u.shm_perm, S_IRUGO)) goto out; id = (unsigned int) shp->u.shm_perm.seq * IPCMNI + shmid; err = -EFAULT; spin_unlock(&shm_lock); if(copy_to_user (buf, &shp->u, sizeof(*buf))) goto out_unlocked; spin_lock(&shm_lock); err = id; goto out; } err = -EINVAL; if ((id = (unsigned int) shmid % IPCMNI) > max_shmid) goto out; if ((shp = shm_segs[id]) == IPC_UNUSED || shp == IPC_NOID) goto out; err = -EIDRM; if (shp->u.shm_perm.seq != (unsigned int) shmid / IPCMNI) goto out; ipcp = &shp->u.shm_perm; switch (cmd) { case SHM_UNLOCK: err = -EPERM; if (!capable(CAP_IPC_LOCK)) goto out; err = -EINVAL; if (!(ipcp->mode & SHM_LOCKED)) goto out; ipcp->mode &= ~SHM_LOCKED; break; case SHM_LOCK: /* Allow superuser to lock segment in memory */ /* Should the pages be faulted in here or leave it to user? */ /* need to determine interaction with current->swappable */ err = -EPERM; if (!capable(CAP_IPC_LOCK)) goto out; err = -EINVAL; if (ipcp->mode & SHM_LOCKED) goto out; ipcp->mode |= SHM_LOCKED; break; case IPC_STAT: err = -EACCES; if (ipcperms (ipcp, S_IRUGO)) goto out; err = -EFAULT; spin_unlock(&shm_lock); if(copy_to_user (buf, &shp->u, sizeof(shp->u))) goto out_unlocked; spin_lock(&shm_lock); break; case IPC_SET: if (current->euid == shp->u.shm_perm.uid || current->euid == shp->u.shm_perm.cuid || capable(CAP_SYS_ADMIN)) { ipcp->uid = tbuf.shm_perm.uid; ipcp->gid = tbuf.shm_perm.gid; ipcp->mode = (ipcp->mode & ~S_IRWXUGO) | (tbuf.shm_perm.mode & S_IRWXUGO); shp->u.shm_ctime = CURRENT_TIME; break; } err = -EPERM; goto out; case IPC_RMID: if (current->euid == shp->u.shm_perm.uid || current->euid == shp->u.shm_perm.cuid || capable(CAP_SYS_ADMIN)) { shp->u.shm_perm.mode |= SHM_DEST; if (shp->u.shm_nattch <= 0) killseg (id); break; } err = -EPERM; goto out; default: err = -EINVAL; goto out; } err = 0; out: spin_unlock(&shm_lock); out_unlocked: return err; } /* * The per process internal structure for managing segments is * `struct vm_area_struct'. * A shmat will add to and shmdt will remove from the list. * shmd->vm_mm the attacher * shmd->vm_start virt addr of attach, multiple of SHMLBA * shmd->vm_end multiple of SHMLBA * shmd->vm_next next attach for task * shmd->vm_next_share next attach for segment * shmd->vm_pgoff offset into segment (in pages) * shmd->vm_private_data signature for this attach */ static struct vm_operations_struct shm_vm_ops = { shm_open, /* open - callback for a new vm-area open */ shm_close, /* close - callback for when the vm-area is released */ NULL, /* no need to sync pages at unmap */ NULL, /* protect */ NULL, /* sync */ NULL, /* advise */ shm_nopage, /* nopage */ NULL, /* wppage */ shm_swapout /* swapout */ }; /* Insert shmd into the list shp->attaches */ static inline void insert_attach (struct shmid_kernel * shp, struct vm_area_struct * shmd) { if((shmd->vm_next_share = shp->attaches) != NULL) shp->attaches->vm_pprev_share = &shmd->vm_next_share; shp->attaches = shmd; shmd->vm_pprev_share = &shp->attaches; } /* Remove shmd from list shp->attaches */ static inline void remove_attach (struct shmid_kernel * shp, struct vm_area_struct * shmd) { if(shmd->vm_next_share) shmd->vm_next_share->vm_pprev_share = shmd->vm_pprev_share; *shmd->vm_pprev_share = shmd->vm_next_share; } /* * ensure page tables exist * mark page table entries with shm_sgn. */ static int shm_map (struct vm_area_struct *shmd) { unsigned long tmp; /* clear old mappings */ do_munmap(shmd->vm_start, shmd->vm_end - shmd->vm_start); /* add new mapping */ tmp = shmd->vm_end - shmd->vm_start; if((current->mm->total_vm << PAGE_SHIFT) + tmp > (unsigned long) current->rlim[RLIMIT_AS].rlim_cur) return -ENOMEM; current->mm->total_vm += tmp >> PAGE_SHIFT; vmlist_modify_lock(current->mm); insert_vm_struct(current->mm, shmd); merge_segments(current->mm, shmd->vm_start, shmd->vm_end); vmlist_modify_unlock(current->mm); return 0; } /* * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists. */ asmlinkage long sys_shmat (int shmid, char *shmaddr, int shmflg, ulong *raddr) { struct shmid_kernel *shp; struct vm_area_struct *shmd; int err = -EINVAL; unsigned int id; unsigned long addr; unsigned long len; down(¤t->mm->mmap_sem); spin_lock(&shm_lock); if (shmid < 0) goto out; shp = shm_segs[id = (unsigned int) shmid % IPCMNI]; if (shp == IPC_UNUSED || shp == IPC_NOID) goto out; if (!(addr = (ulong) shmaddr)) { if (shmflg & SHM_REMAP) goto out; err = -ENOMEM; addr = 0; again: if (!(addr = get_unmapped_area(addr, (unsigned long)shp->u.shm_segsz))) goto out; if(addr & (SHMLBA - 1)) { addr = (addr + (SHMLBA - 1)) & ~(SHMLBA - 1); goto again; } } else if (addr & (SHMLBA-1)) { if (shmflg & SHM_RND) addr &= ~(SHMLBA-1); /* round down */ else goto out; } /* * Check if addr exceeds TASK_SIZE (from do_mmap) */ len = PAGE_SIZE*shp->shm_npages; err = -EINVAL; if (addr >= TASK_SIZE || len > TASK_SIZE || addr > TASK_SIZE - len) goto out; /* * If shm segment goes below stack, make sure there is some * space left for the stack to grow (presently 4 pages). */ if (addr < current->mm->start_stack && addr > current->mm->start_stack - PAGE_SIZE*(shp->shm_npages + 4)) goto out; if (!(shmflg & SHM_REMAP) && find_vma_intersection(current->mm, addr, addr + (unsigned long)shp->u.shm_segsz)) goto out; err = -EACCES; if (ipcperms(&shp->u.shm_perm, shmflg & SHM_RDONLY ? S_IRUGO : S_IRUGO|S_IWUGO)) goto out; err = -EIDRM; if (shp->u.shm_perm.seq != (unsigned int) shmid / IPCMNI) goto out; spin_unlock(&shm_lock); err = -ENOMEM; shmd = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); spin_lock(&shm_lock); if (!shmd) goto out; if ((shp != shm_segs[id]) || (shp->u.shm_perm.seq != (unsigned int) shmid / IPCMNI)) { kmem_cache_free(vm_area_cachep, shmd); err = -EIDRM; goto out; } shmd->vm_private_data = shm_segs[id]; shmd->vm_start = addr; shmd->vm_end = addr + shp->shm_npages * PAGE_SIZE; shmd->vm_mm = current->mm; shmd->vm_page_prot = (shmflg & SHM_RDONLY) ? PAGE_READONLY : PAGE_SHARED; shmd->vm_flags = VM_SHM | VM_MAYSHARE | VM_SHARED | VM_MAYREAD | VM_MAYEXEC | VM_READ | VM_EXEC | ((shmflg & SHM_RDONLY) ? 0 : VM_MAYWRITE | VM_WRITE); shmd->vm_file = NULL; shmd->vm_pgoff = 0; shmd->vm_ops = &shm_vm_ops; shp->u.shm_nattch++; /* prevent destruction */ spin_unlock(&shm_lock); err = shm_map (shmd); spin_lock(&shm_lock); if (err) goto failed_shm_map; insert_attach(shp,shmd); /* insert shmd into shp->attaches */ shp->u.shm_lpid = current->pid; shp->u.shm_atime = CURRENT_TIME; *raddr = addr; err = 0; out: spin_unlock(&shm_lock); up(¤t->mm->mmap_sem); return err; failed_shm_map: if (--shp->u.shm_nattch <= 0 && shp->u.shm_perm.mode & SHM_DEST) killseg(id); spin_unlock(&shm_lock); up(¤t->mm->mmap_sem); kmem_cache_free(vm_area_cachep, shmd); return err; } /* This is called by fork, once for every shm attach. */ static void shm_open (struct vm_area_struct *shmd) { struct shmid_kernel *shp; spin_lock(&shm_lock); shp = (struct shmid_kernel *) shmd->vm_private_data; insert_attach(shp,shmd); /* insert shmd into shp->attaches */ shp->u.shm_nattch++; shp->u.shm_atime = CURRENT_TIME; shp->u.shm_lpid = current->pid; spin_unlock(&shm_lock); } /* * remove the attach descriptor shmd. * free memory for segment if it is marked destroyed. * The descriptor has already been removed from the current->mm->mmap list * and will later be kfree()d. */ static void shm_close (struct vm_area_struct *shmd) { struct shmid_kernel *shp; spin_lock(&shm_lock); /* remove from the list of attaches of the shm segment */ shp = (struct shmid_kernel *) shmd->vm_private_data; remove_attach(shp,shmd); /* remove from shp->attaches */ shp->u.shm_lpid = current->pid; shp->u.shm_dtime = CURRENT_TIME; if (--shp->u.shm_nattch <= 0 && shp->u.shm_perm.mode & SHM_DEST) killseg (shp->id); spin_unlock(&shm_lock); } /* * detach and kill segment if marked destroyed. * The work is done in shm_close. */ asmlinkage long sys_shmdt (char *shmaddr) { struct vm_area_struct *shmd, *shmdnext; down(¤t->mm->mmap_sem); for (shmd = current->mm->mmap; shmd; shmd = shmdnext) { shmdnext = shmd->vm_next; if (shmd->vm_ops == &shm_vm_ops && shmd->vm_start - (shmd->vm_pgoff << PAGE_SHIFT) == (ulong) shmaddr) do_munmap(shmd->vm_start, shmd->vm_end - shmd->vm_start); } up(¤t->mm->mmap_sem); return 0; } /* * Enter the shm page into the SHM data structures. * * The way "nopage" is done, we don't actually have to * do anything here: nopage will have filled in the shm * data structures already, and shm_swap_out() will just * work off them.. */ static int shm_swapout(struct page * page, struct file *file) { return 0; } /* * page not present ... go through shm_dir */ static struct page * shm_nopage(struct vm_area_struct * shmd, unsigned long address, int no_share) { pte_t pte; struct shmid_kernel *shp; unsigned int idx; struct page * page; shp = (struct shmid_kernel *) shmd->vm_private_data; idx = (address - shmd->vm_start) >> PAGE_SHIFT; idx += shmd->vm_pgoff; down(&shp->sem); spin_lock(&shm_lock); pte = SHM_ENTRY(shp,idx); if (!pte_present(pte)) { /* page not present so shm_swap can't race with us and the semaphore protects us by other tasks that could potentially fault on our pte under us */ if (pte_none(pte)) { spin_unlock(&shm_lock); page = alloc_page(GFP_HIGHUSER); if (!page) goto oom; clear_highpage(page); spin_lock(&shm_lock); } else { swp_entry_t entry = pte_to_swp_entry(pte); spin_unlock(&shm_lock); page = lookup_swap_cache(entry); if (!page) { lock_kernel(); swapin_readahead(entry); page = read_swap_cache(entry); unlock_kernel(); if (!page) goto oom; } delete_from_swap_cache(page); page = replace_with_highmem(page); lock_kernel(); swap_free(entry); unlock_kernel(); spin_lock(&shm_lock); shm_swp--; } shm_rss++; pte = pte_mkdirty(mk_pte(page, PAGE_SHARED)); SHM_ENTRY(shp, idx) = pte; } else --current->maj_flt; /* was incremented in do_no_page */ /* pte_val(pte) == SHM_ENTRY (shp, idx) */ get_page(pte_page(pte)); spin_unlock(&shm_lock); up(&shp->sem); current->min_flt++; return pte_page(pte); oom: up(&shp->sem); return NOPAGE_OOM; } /* * Goes through counter = (shm_rss >> prio) present shm pages. */ static unsigned long swap_id = 0; /* currently being swapped */ static unsigned long swap_idx = 0; /* next to swap */ int shm_swap (int prio, int gfp_mask) { pte_t page; struct shmid_kernel *shp; swp_entry_t swap_entry; unsigned long id, idx; int loop = 0; int counter; struct page * page_map; counter = shm_rss >> prio; if (!counter) return 0; lock_kernel(); /* subtle: preload the swap count for the swap cache. We can't increase the count inside the critical section as we can't release the shm_lock there. And we can't acquire the big lock with the shm_lock held (otherwise we would deadlock too easily). */ swap_entry = __get_swap_page(2); if (!swap_entry.val) { unlock_kernel(); return 0; } unlock_kernel(); spin_lock(&shm_lock); check_id: shp = shm_segs[swap_id]; if (shp == IPC_UNUSED || shp == IPC_NOID || shp->u.shm_perm.mode & SHM_LOCKED ) { next_id: swap_idx = 0; if (++swap_id > max_shmid) { swap_id = 0; if (loop) goto failed; loop = 1; } goto check_id; } id = swap_id; check_table: idx = swap_idx++; if (idx >= shp->shm_npages) goto next_id; page = SHM_ENTRY(shp, idx); if (!pte_present(page)) goto check_table; page_map = pte_page(page); if ((gfp_mask & __GFP_DMA) && !PageDMA(page_map)) goto check_table; if (!(gfp_mask & __GFP_HIGHMEM) && PageHighMem(page_map)) goto check_table; swap_attempts++; if (--counter < 0) { /* failed */ failed: spin_unlock(&shm_lock); lock_kernel(); __swap_free(swap_entry, 2); unlock_kernel(); return 0; } if (page_count(page_map) != 1) goto check_table; if (!(page_map = prepare_highmem_swapout(page_map))) goto failed; SHM_ENTRY (shp, idx) = swp_entry_to_pte(swap_entry); swap_successes++; shm_swp++; shm_rss--; /* add the locked page to the swap cache before allowing the swapin path to run lookup_swap_cache(). This avoids reading a not yet uptodate block from disk. NOTE: we just accounted the swap space reference for this swap cache page at __get_swap_page() time. */ add_to_swap_cache(page_map, swap_entry); spin_unlock(&shm_lock); lock_kernel(); rw_swap_page(WRITE, page_map, 0); unlock_kernel(); __free_page(page_map); return 1; } /* * Free the swap entry and set the new pte for the shm page. */ static void shm_unuse_page(struct shmid_kernel *shp, unsigned long idx, swp_entry_t entry, struct page *page) { pte_t pte; pte = pte_mkdirty(mk_pte(page, PAGE_SHARED)); SHM_ENTRY(shp, idx) = pte; get_page(page); shm_rss++; shm_swp--; spin_unlock(&shm_lock); lock_kernel(); swap_free(entry); unlock_kernel(); } /* * unuse_shm() search for an eventually swapped out shm page. */ void shm_unuse(swp_entry_t entry, struct page *page) { int i, n; spin_lock(&shm_lock); for (i = 0; i <= max_shmid; i++) { struct shmid_kernel *seg = shm_segs[i]; if ((seg == IPC_UNUSED) || (seg == IPC_NOID)) continue; for (n = 0; n < seg->shm_npages; n++) { if (pte_none(SHM_ENTRY(seg,n))) continue; if (pte_present(SHM_ENTRY(seg,n))) continue; if (pte_to_swp_entry(SHM_ENTRY(seg,n)).val == entry.val) { shm_unuse_page(seg, n, entry, page); return; } } } spin_unlock(&shm_lock); } #ifdef CONFIG_PROC_FS static int sysvipc_shm_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data) { off_t pos = 0; off_t begin = 0; int i, len = 0; len += sprintf(buffer, " key shmid perms size cpid lpid nattch uid gid cuid cgid atime dtime ctime\n"); spin_lock(&shm_lock); for(i = 0; i <= max_shmid; i++) if(shm_segs[i] != IPC_UNUSED) { #define SMALL_STRING "%10d %10d %4o %10u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n" #define BIG_STRING "%10d %10d %4o %21u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n" char *format; if (sizeof(size_t) <= sizeof(int)) format = SMALL_STRING; else format = BIG_STRING; len += sprintf(buffer + len, format, shm_segs[i]->u.shm_perm.key, shm_segs[i]->u.shm_perm.seq * IPCMNI + i, shm_segs[i]->u.shm_perm.mode, shm_segs[i]->u.shm_segsz, shm_segs[i]->u.shm_cpid, shm_segs[i]->u.shm_lpid, shm_segs[i]->u.shm_nattch, shm_segs[i]->u.shm_perm.uid, shm_segs[i]->u.shm_perm.gid, shm_segs[i]->u.shm_perm.cuid, shm_segs[i]->u.shm_perm.cgid, shm_segs[i]->u.shm_atime, shm_segs[i]->u.shm_dtime, shm_segs[i]->u.shm_ctime); pos += len; if(pos < offset) { len = 0; begin = pos; } if(pos > offset + length) goto done; } *eof = 1; done: *start = buffer + (offset - begin); len -= (offset - begin); if(len > length) len = length; if(len < 0) len = 0; spin_unlock(&shm_lock); return len; } #endif